Khloe Kardashian has previously insisted that she is the biological daughter of the late Robert Kardashian, but a tabloid claims to have discovered the identity of a man it believes is the reality TV star's real father.

Alex Roldan, who bears a striking resemblance to Kardashian, is rumored to be the biological father of Kardashian, 28. The Los Angeles-based hairdresser, who spent 30 years working for Kardashian matriarch Kris Jenner, reportedly signed a non-disclosure agreement at Jenner's request which prohibits him from ever discussing Kardashian's paternity.

"He has been brought up by Kris so he can't speak," a source told In Touch magazine."He has an NDA (non-disclosure agreement) [that] makes him liable for $30 million if he ever talks to the press."

For years, critics, including Robert's ex-wife Jan Ashley, have openly doubted that the famed attorney is the biological father of Kardashian.

"Khloe is not his kid," Ashley previously told Star magazine, referring to her ex-husband. "He told me that after we got married. He just kind of looked at me and said it like it was a matter of fact."

The Kardashian sisters are known for their exotic features, which includes dark hair and dark eyes, and critics have long pointed out how different Khloe looks to her sisters Kim and Kourtney. The reality TV star has allegedly always had doubts about whether Robert is her real father.

"When she was younger, Kim and Kourtney would tease her that she's adopted because she's blonde and so tall," a source said adding "Khloé just doesn't fit in physically."

Robert's widow, Ellen Kardashian, also expressed doubts about Kardashian's paternity issue, claiming Robert was doubtful that he was Khloe's biological father.

"Khloe brought it up all the time. ... She looked nothing like the rest. She was tall, had a different shape, light hair, curly hair. Didn't look anything like the other three children," Ellen said.

"Robert did question the fact that Khloe was his. ... Any normal man would if they knew their wife had cheated on him," she added.

Kardashian previously blasted both women, describing their allegations as "disgusting."

"The audacity you have to mention my father's name like this. Should be ashamed of urself [sic] … I let a lot of things slide but this one is really low. YOU ARE DISGUSTING," she tweeted previously.